The choice of bottle closures – the final choice of the winemaker

Winemaking is a progressive process and winemakers have to make different decisions in the course thereof until the wine eventually reaches the glass of the consumer. Depending on the wine style and type, this period can last from months to years. The final bottling of the wine does, however, take only a couple of hours, during which all the devotion of years can be rewarded or shattered. The choice of bottle closure is one of the factors that can make a difference.

Vineyards are selected by winemakers to obtain specific aims and the grapes are harvested at optimal ripeness as the first step in the winemaking process. The fermentation strategy, maturation programme and stabilisation procedures are further decisions taken before wines are bottled. In a previous article, the different closures that can be used, were discussed (Theron, 2016).

In order to ascertain the viewpoints and experience of winemakers regarding the topic, three Californian winemakers were approached for their comments. Marco DiGiulio of Vintage Wine Estate, Michael Carr of Roche Winery & Vineyards and Mike Cox, previously from Schug Carneros Estate, share years of experience in winemaking. Depending on their individual experience with different bottle closures and the wine portfolio that is applicable, winemakers differ regarding their choice of the best bottle closure. Natural cork was for many years the chosen bottle closure and it still remains so. Unfortunately it has a few unique problems. Depending on the production processes that are used, it can impart a mouldy character to wine in the form of trichloro-anisole (TCA). From 1980 to the 1990s the problem was so serious that up to 15% of natural corks were contaminated. Suppliers of natural corks, however, decreased the occurrence of the problem considerably through innovative actions. Seeing that it is a natural product, the oxygen permeability of individual corks differs, which can influence the bottle maturation process. A variation between individual corks will consequently remain. These two problems created a great opportunity for alternative bottle closures. As described in the above-mentioned article, these varied from synthetic closures made from plastic compounds, agglomerated corks made from compressed glued cork particles, bio-tech closures made from cane sugar to even glass closures. Each closure has its own unique problems, apart from the oxygen transmission rate (OTR), which is an universal potential problem. Excessive permeated oxygen can lead to oxidation and limited permeated oxygen can lead to reductive flavours. Natural cork has, however, remained the most popular closure, especially for wines having five years bottle maturation.

The popularity of technical bottle closures, like Diam and bio-tech closures like Nomacorc, increased considerably, mainly as result of better control of the OTR of these products. Screw closures are especially popular for wines, which are drunk shortly after bottling. Conclusively it can be stated that winemakers base their decision about bottle closures on their experience with different bottle closures. This benefits natural cork, because it is known for a long time, it is related to tradition and the romantics associated with pulling a cork. Some consumers also associate natural cork with better wines. This applies especially to consumers older than 50 years, while younger consumers below 30 years are willing to experiment with alternative bottle closures, seeing that they judge it only for the primary reason for closing the bottle. Winemakers consequently have different viewpoints for their decision and base it mainly on their personal experience (Cutler, 2018).